High-voltage transformers for power supply systems with a voltage level of greater than or equal to 110 kV can be arranged in an oil-filled transformer tank for insulation and for better dissipation of waste heat produced during operation. The external electrical terminals can be arranged in the form of corresponding leadouts on the transformer tank.
In order to electrically connect end windings of transformer windings of the high-voltage transformer which are located in a transformer tank to the leadouts, respective electrical connecting conductors are passed through the oil-filled transformer tank. This can result in the connecting conductor diameter being relatively small, for example, a few cm. It may also be desirable for the conductor to be passed close to adjoining component parts with a high electrical potential difference, for example core-press parts or a further winding, for reasons of space. There can be a risk of undesirable flashovers or at least partial discharges when a corresponding electric field intensity is exceeded in regions.
In this respect, it is known to surround the respective connecting conductor with a lead-out tube along the extent of the connecting conductor. The lead-out tube can limit the maximum electrical field strength. A lead-out tube has an inner shielding tube of a conductive material, with the connecting conductor arranged in an interior of the shielding tube. The shielding tube is at the same electrical potential as the conductor passing through it during operation of the transformer, with the result that there is no potential difference between the connecting conductor and the shielding tube and a flashover or a partial discharge may not occur within the shielding tube.
The shielding tube can either be insulated by a thick single-ply insulating layer or can be surrounded by a plurality of barriers including an insulating material which are arranged hollow-cylindrically around the shielding tube and are radially adjacent to one another. In each case a space for the passage of transformer oil is provided between the barriers. The variant with insulating barriers can have electrical advantages over a single-ply insulating layer.
The manufacture of barriers with sectionally curved shielding tubes can be work-intensive. Lead-out tubes can be considered as individually manufactured products because power transformers with an identical design are manufactured in low numbers. Owing to improved space utilization within the transformer tank, even a plurality of points of curvature can be provided.
A modular system of component parts for the barriers of lead-out tubes has been used, with no more than one point of curvature of 90°. It is also possible for especially manufactured half-shell parts to be manufactured for the barriers, whereby a plurality of curvatures can be realized but a considerable degree of production complexity is involved for corresponding forms for a manufacture of the half-shell parts. Owing to the abovementioned rare manufacture of transformers of identical design, however, even the production of an individual form can involve an undesirably high level of complexity. In addition, an electrical weak point in the barrier results at the points of overlap between mutually adjoining modules or half-shells.